Kestrel is most commonly the name for a small, hovering bird of prey in the falcon family, but the word is also used for several tech tools and projects.

What is a kestrel (bird)?

  • A kestrel is a small falcon in the genus Falco , best known for its ability to hover over open ground while searching for prey.
  • These birds typically hunt small mammals, lizards, and large insects, swooping down after hovering 10–20 meters above the ground.

Key bird facts

  • Kestrels show color differences between males and females; males are usually more brightly colored, which is unusual among hawks.
  • The American kestrel (Falco sparverius) is widespread in the Americas, while the common/European kestrel (Falco tinnunculus) is found across much of the Old World.

Other meanings of “Kestrel”

  • In software, Kestrel is the default cross‑platform web server used by ASP.NET Core applications from Microsoft, designed to be fast and lightweight.
  • There is also a Kestrel threat‑hunting language from the Open Cybersecurity Alliance, used to express reusable threat‑hunting logic across different security data sources.

Older tech usage

  • Kestrel was the name of a simple, distributed message queue system originally used at Twitter and now archived, offering queue operations over text and memcache‑style protocols.

SEO meta description

Kestrel is primarily a small hovering falcon, but the name also refers to modern tech projects such as Microsoft’s ASP.NET Core web server and a cybersecurity threat‑hunting language, making “what is kestrel” a multi‑context question.

Information gathered from public forums or data available on the internet and portrayed here.